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UJI AKTIVITAS ANTIOKSIDAN FRAKSI AIR DAN FRAKSI ETER KOMBINASI EKSTRAK METANOL DAUN KOPI ARABIKA (Coffea arabica) DAN KELOPAK BUNGA ROSELLA (Hibiscus sabdariffa)
No full textDalam kehidupan sehari-hari, kita tidak dapat terbebas dari senyawa radikal bebas. Radikal bebas merupakan molekul yang memiliki satu atau lebih elektron yang tidak berpasangan. Seperti yang kita ketahui bahwa beberapa penyakit seperti cardiovascular heart disease, diabetes melitus, dan kanker merupakan penyakit yang dipicu oleh kerusakan oksidatif dengan adanya radikal bebas.
Antioksidan adalah molekul yang mampu menghambat kerusakan oksidatif yang dihasilkan radikal bebas. Antioksidan merupakan suatu senyawa yang memiliki kemampuan untuk bereaksi dengan radikal bebas menghasilkan suatu radikal bebas yang stabil dengan cara menerima atau menyumbangkan elektronnya.
Kopi Arabika (Coffea arabica) merupakan bahan minuman yang terkenal tidak hanya di Indonesia tetapi juga terkenal di seluruh dunia. Didalam tanaman kopi Arabika terdapat senyawa polifenol merupakan antioksidan alami yang banyak dijumpai dalam asupan makanan sehari-hari. Selain itu, saat ini tanaman rosella (Hibiscus sabdariffa) menjadi begitu populer. Hampir di setiap pameran tanaman obat, nama rosella selalu diperkenalkan. Menurut hasil penelitian sebelumnya menunjukkan bahwa kandungan asam askorbat (vitamin C) dan antosianin pada tanaman ini merupakan sumber antioksidan alami yang sangat efektif dalam menangkal berbagai radikal bebas.
Dalam upaya mendapatkan suatu sediaan obat herbal yang kaya akan kandungan antioksidan maka pada penelitian ini akan dilakukan penentuan aktivitas antioksidan kombinasi daun Kopi Arabika dan kelopak bunga rosella. Tujuan dari penelitian ini adalah untuk mengetahui aktivitas antioksidan (IC50) fraksi air dan fraksi eter ekstrak metanol daun kopi Arabika (Coffea arabica) dan ekstrak metanol kelopak bunga rosella (Hibiscus sabdariffa) serta kombinasi keduanya.
Penelitian ini dilakukan di laboratorium bagian biologi dan kimia Fakultas Farmasi Universitas Jember. Kegiatan yang dilakukan dalam penelitian ini meliputi pembuatan simplisia, ekstraksi simplisia, standarisasi simplisia dan ekstrak, fraksinasi dan pengujian aktivitas antioksidan.
Pengujian aktivitas antioksidan dilakukan dengan menggunakan metode DPPH. Metode DPPH (1,1-diphenyl-2-picrylhydrazyl) merupakan metode yang paling sering digunakan untuk menguji aktivitas antioksidan tanaman obat. Tujuan metode ini adalah mengetahui parameter konsentrasi yang ekuivalen memberikan 50% efek aktivitas antioksidan (IC50). Pada pengujian yang dilakukan aktivitas antioksidan terbesar yaitu fraksi air ekstrak metanol daun kopi Arabika dengan nilai IC50 26,201 ± 0,323 μg/ml disusul fraksi eter ekstrak metanol kelopak bunga rosella, fraksi eter ekstrak metanol daun kopi Arabika dan fraksi air ekstrak metanol kelopak bunga rosella dengan nilai IC50 62,407 ± 0,541 μg/ml; 73,321 ± 0,241 μg/ml; dan 230,560 ± 0,967 μg/ml.
Hasil uji One way anova menunjukkan nilai signifikansi ≤ 0,05 dengan taraf kepercayaan 95% maka dapat dikatakan bahwa ada perbedaan aktivitas antioksidan yang bermakna antara bentuk tunggal dan kombinasi. Hasil uji Post hoc (LSD) menunjukkan nilai signifikansi ≤ 0,05 dengan taraf kepercayaan 95% maka dapat dikatakan bahwa nilai aktivitas antioksidan pada setiap sampel berbeda secara bermakna jika dibandingkan dengan sampel lain
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
STUDY OF ANTIOXIDANT ACTIVITY COMBINATION OF ARABICA COFFEE LEAF ETHANOL EXTRACT AND ROSELLE FLOWER PETAL WATER EXTRACT
No full textFree radicals are molecules that have one or more
unpaired electrons. As we know that some
cardiovascular diseases such as heart disease,
diabetes mellitus, and cancer are diseases that
triggered by oxidative damage in the presence of
free radicals. Excessive oxidation of the nucleic
acids, proteins, fats and DNA cells can initiate the
occurrence of degenerative diseases such as
coronary heart disease, cataracts, cognitive
disorders and cancer (Leong and Shui, 2001; Pietta
1999). Humans have had a defense system against
oxidants that come from within or from outside the
body in the form of diet. Defense of the body such
as enzymes peroxidase, catalase, glutathione,
histidine, peptidin often still lacking due to
environmental influences and poor diet (Pietta,
1999).
Antioxidants are molecules that can inhibit the
oxidation of molecules that can produce free
radicals. Antioxidant is a compound that has the
ability to react with free radicals to produce a stable
free radical by accepting or donating electrons.
Based on the source of, antioxidant divided into two
kinds, namely natural antioxidants and antioxidants
synthetic (artificial). Synthetic antioxidants are most
often used such as Propyl Error (PG), Butylated
hydroxyanisole (BHA), Butylated hydroxytoluene
(BHT) and Tertbutylhydroquinone (TBHQ). The
synthetic antioxidants can give side effects that
harmful to human health because it’s carcinogenic.
Various studies on BHA and BHT indicate that this
can cause tumors in laboratory animals at long-term
use (Kikuzaki, 1993). Natural antioxidant is an
antioxidant that is obtained naturally in plants.
Natural antioxidants are usually more desirable,
because the level of better security and broader
benefits in the food, health and cosmetics. Natural
antioxidants can be found in food of vegetables and
fruits. As an example of natural antioxidants such as
Vitamin A, Vitamin C, Vitamin E, and Polyphenols.
Their concerns about the potential side effects of
synthetic antioxidants used as motivation for the
study of natural antioxidants as one alternative
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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